Rotational viscometers require a rotating element called the rotor and a stationary element called the stator, which contains the fluid to be tested for properties such as viscosity, and in which most typically the rotor rotates in contact with the fluid so as to determine drag caused by the liquid. This drag can then be related to the viscosity.
Sensitive rotational viscometers such as the Brookfield viscometer are well-known instruments for measuring viscosities of liquids. Usually, the rotor, which is driven by a motor in the Brookfield head, is immersed in a large container of liquid in which the walls of the container are at some considerable distance from the rotor and thus have little influence on the measurement of the viscous value. This container is the stator. In some applications such as in the well-known ASTM D 2983, which tests the viscosity of gear oil at low temperature, the rotor must be radially and vertically aligned to gain the necessary accuracy. What is more, since the apparent viscosity of the tested fluid, a factor of the amount of torque or drag exerted on the rotor by the fluid in contact with it, is proportional to the extent to which the rotor is immersed in the fluid, any vertical, i.e., up and down, movement of the rotor in the test fluid will alter the torque and thus the viscosity readout. Thus, the instrument must be balanced carefully and supported firmly, not only from radial displacement but also especially from vertical movement.
In practice, problems are encountered with commercially available Brookfield viscometers such as the so-called "Top Hat" type viscometer, which is known commercially as the Brookfield Dial Reading Viscometer, and Brookfield Digital Display Viscometer, DV- & LV-series models. In particular, the fine balance required for the ASTM D 2983 test can be hard to acquire so as to obtain accurate results, and there often is encountered unacceptable vertical movement with the instrument, to make for additionally inaccurate readout.
What is needed is an improvement which overcomes such problems, while providing for precise radial and vertical balance of the sensitive rotating viscometer and its rotor. It should be readily manufacturable and commercializable--and efficient to operate, even by inexperienced operators. Desirably, it might also be applicable in further fields.